Analyzing mRNA level in cells within the cerebrospinal fluid (CSF) of patients with SAH compared to patients without hemorrhage, we found significantly greater induction of HO-1 compared to the HO-2 isoform and the enzyme biliverdin reductase A as the downstream enzyme responsible for heme degradation (BLVRA, Figure 6a,b). Here, HMOX1 is linked to hemorrhage.